Kaustinen (Swedish:Kaustby) is a municipality of Finland.
It is part of the Central Ostrobothnia region. The municipality has a population of 4,287 (30 June 2015) and covers an area of 361.12 square kilometres (139.43sqmi) of which 7.09km (2.74sqmi) is water. The population density is 12.11 inhabitants per square kilometre (31.4/sqmi).